The Hawker Siddeley P.1154 was a planned supersonic vertical/short take-off and landing (V/STOL) fighter aircraft designed by Hawker Siddeley Aviation (HSA).
Development originally started under P.1150, which was essentially a larger and faster version of the basic layout and technology being developed by the smaller subsonic Hawker Siddeley P.1127/Kestrel. A key difference of this design was the addition of plenum chamber burning, essentially an afterburner-like arrangement in the thrusters used during hover, greatly increasing their thrust.
The release of NATO Basic Military Requirement 3 for a VTOL strike-fighter led to widespread industry participation. Hawker felt the P.1150 did not meet the requirements, so it was enlarged to become P.1150/3, and then renamed P.1154. This Mach 2-capable aircraft was the technical winner of the eleven submissions for NBMR-3, with the Dassault Mirage IIIV selected as a second design. Political infighting between the two groups and their various supporters, along with continual changing of the strategic environment, led to neither project progressing into production.
Meanwhile, Hawker Siddeley considered modifying the airframe for a joint specification for an aircraft by the RAF and Royal Navy. Between 1961 and 1965 the two services harmonised their specifications to preserve design commonality. However, the RAF's desired configuration was to take precedence over that of the Royal Navy's. A number of proposals were submitted; at one stage, a twin-Spey design was considered, then rejected. Following the Labour government's coming to power the project was cancelled in 1965. The Royal Navy would acquire the McDonnell Douglas F-4 Phantom II, while the RAF continued to foster development of the P.1127 (RAF), leading to the successful Harrier family.
Development
Background
During the late 1950s, Hawker Siddeley Aviation (HSA) was keen to develop a new generation of combat aircraft that would be capable of supersonic speeds. Unfortunately, despite repeated attempts to revive the program, the in-development Hawker P.1121 fighter would ultimately be left unfinished, principally due to a lack of a political support for development following the release of the 1957 Defence White Paper by Minister of Defence Duncan Sandys. Recognising the need to promptly commence work on another development program, HSA's chief aircraft designer Sir Sydney Camm, who had been in regular discussions with Sir Stanley Hooker of Bristol Aero Engines, decided that the company should investigate the prospects of developing and manufacturing a viable combat-capable vertical take-off and landing (VTOL) fighter aircraft.
Bristol Aero Engines and Hooker had already been working on a project to produce a suitable VTOL engine; this engine combined major elements of their Olympus and Orpheus jet engines to produce a directable fan jet. The projected fan jet harnessed rotatable cold jets which were positioned on either side of the compressor along with rotatable 'hot' jets which was directed via a bifurcated tailpipe. With a suitable engine already being developed, Camm and his team at HSA proceeded to develop the company's first VTOL aircraft, designated as the Hawker Siddeley P.1127. The P.1127 was envisioned as a subsonic VTOL-capable strike aircraft, while also serving to demonstrate and prove the capabilities of the aircraft's basic configuration and to validate the performance of the Rolls-Royce Pegasus engine that powered it.
While financial backing was issued by NATO's Mutual Weapons Development Program to support development of the Pegasus engine, the British government were not forthcoming with funding. While HSA chose to go ahead with the P.1127 as a private venture, the Air Staff disagreed heavily over what requirements should be set out for a future RAF VTOL aircraft; some officers, such as the Chief of the Air Staff Sir Thomas Pike, advocated simplicity while others, such as the RAF operational requirements division, sought various performance demands of such an aircraft, particularly the capacity for supersonic flight. HSA was also interested in the prospects and feasibility of a more sophisticated development of the P.1127, knowing that a supersonic-capable VTOL aircraft would likely be more attractive to customers, there being a general perception at the time that supersonic aircraft held significantly more value than their subsonic counterparts.